`quantity_parametric.Rd`

For a parametric distribution, evaluates a quantity
(such as mean, median, range, ...) if the distribution has
an entry in the `.quantities`

database. For distributions without
the "parametric" (sub-) class, quantity evaluation is delegated
to the next higher level class.

`quantity_parametric(distribution, quantity)`

- distribution
A distribution.

- quantity
Character; name of the quantity to extract.

The desired quantity, evaluated.